A CRDT Supporting Selective Undo for Collaborative Text Editing

Abstract

International audienceUndo is an important feature of editors. However, even after over two decades of active research and development, support of undo for real-time col-laborative editing is still very limited. We examine issues concerning undo in collaborative text editing and present an approach using a layered commutative replicated data type (CRDT). Our performance study shows that it provides sufficient responsiveness to the end users

Handling Disturbance and Awareness of Concurrent Updates in a Collaborative Editor

“…This make Emacs very suitable for customization and extension. We have earlier implemented the view and the CRDT model described in Section 2 in Emacs Lisp [16]. We have also implemented support for selective undo and selection of updates through a history view.…”

“…We refer the interested readers to [16] for more details on the data structure and algorithms on the model. Materialization of editing operations in the model makes a number of tasks easier, including support for selective undo and handling of operation dependencies [16], as well as user friendliness features like display of operation history and selection of operations to undo or redo, and preview of concurrent remote operations as described in the following sections.…”

“…However, for these different purposes, we must transform the operations differently. With CRDT, the effect of an integration is materialized in the data structure, which can be used for different purposes, such as for selective undo [16] and for focus regions. To detect whether a remote update falls inside a focus region, we only need to compare the character identifiers of the operation and of the region.…”

“…We have implemented support for collaborative editing in GNU Emacs, using CRDT (Commutative Replicated Data Types) and supporting selective undo [16]. In this paper, we present an experimental feature that lets the user handle the disturbance and awareness of concurrent updates.…”

“…This paper is organized as follows. Section 2 gives a short review on our CRDT approach to real-time collaborative editing [16]. Section 3 presents the new features for handling disturbance and awareness through an example.…”